1. Field of the Invention
The present invention relates to a valve, e.g., attached to an opening of a tank in which a fluid is sealed. The valve is operated to discharge the fluid from the tank by opening/closing a valve plug.
2. Description of the Related Art
A valve has been hitherto generally used to open/close an opening of a tank in which a fluid (for example, xenon gas) is sealed. The valve comprises a body which is connected to an upper end of the tank, a spring which is attached in the body, a valve plug which is displaceable by the spring, and a valve seat on which the valve plug is seated. The valve plug is seated on the valve seat by the spring force, and thus the fluid is kept in the tank gas-tightly. When the valve plug is pressed against the resilient force of the spring, the valve is opened, in which the fluid in the tank is discharged outside.
In the conventional valve as described above, the valve plug is seated on the valve seat by the resilient force of the spring to keep the fluid in the tank gas-tightly. However, it is demanded to secure the gas-tightness for the fluid even when the fluid in the tank is discharged by opening the valve plug.